EL AGUACATE, Guatemala (AP) -- Agustina Machic still feels scared when she recalls the days in 1988 when her husband and 21 others, many of them her relatives, were killed by suspected rebels who accused them of collaborating with the army as a civil war raged in Guatemala.

"We lost everything, the animals, the house. We were left with no one," the 76-year-old said in a low voice, afraid of being overhead by neighbors she says were allied with the guerrillas and may have participated in the massacre.

Despite lingering fears 25 years later, Machic said she'll testify in a trial that began Thursday, the first against an ex-guerrilla charged with taking part in a massacre during Guatemala's conflict.

As the trial began on Thursday, Solano Barillas told The Associated Press that he is innocent of the charges and hopes that justice will be done.

Past attempts to obtain justice for atrocities during the decades long civil war have focused on the misdeeds by the army.

Now, more than 30 people, including military officers of various ranks, experts and several of the victims' widows, are expected to testify in the trial against Fermin Felipe Solano Barillas in the western city of Chilmatenango.

Solano Barrillas, whose nom de guerre was "Lieutenant David," is a former leader of the Revolutionary Organization of the People in Arms, or ORPA, one of four guerrilla groups that fought against the army during Guatemala's 1960-1996 civil war.

Rebels initially blamed the army for what came to be known as the El Aguacate Massacre, named for the community where it occurred.

But several years after a peace accord ended the conflict in 1996, a UN truth commission determined that rebels were responsible.

The commission said in a 1999 report that 93 percent of the killings during the war, including 626 massacres, were committed by the army and its allies. It attributed 3 percent of the killings to guerrillas, including 32 massacres, among them the one in El Aguacate. The commission couldn't determine responsibility for the other 4 percent.

Solano Barillas' lawyer, Julio Salvador Perez Hernandez, said the charges against his client are politically driven and that authorities have no evidence to back up them up.

The series of civil war-era trials is widely seen as a turning point in a nation still wrestling with the trauma of a conflict that killed about 200,000 people.

Several high-ranking officials have been prosecuted on war-crimes charges. But the highest-ranking, former dictator Efrain Rios Montt, saw his conviction annulled last year in a high court decision that many saw as a sign of the lingering influence of the wartime military and its supporters.

Rios Montt's trial will re-start in January 2015 after the Constitutional Court threw out an earlier 80-year sentence against him for the massacre of thousands of Mayans during his 1982-83 rule.

The massacre in the township of El Aguacate began on Novermber 22, 1988, when leftist rebels allegedly killed Carlos Humberto Guerra Callejas, a civilian liaison with the military in the village 40 miles (65 kilometers) west of Guatemala City.

According to the widows, Guerra Callejas had discovered a place in the mountains that the rebels were using to hide clothes, food and other items and was stealing their supplies.

Three days after he went missing, a group of relatives and friends organized a search party that was ambushed by suspected rebels. A few managed to escape, but 21 were captured, tortured and hanged. Soldiers found Guerra Callejas' body and fought against rebels before unearthing the bodies of the other 21 people buried in clandestine graves.

At least 12 victims were related to Guerra Callejas.

"All of those who died were family. Uncles, cousins, brothers. They left us all alone," Machic said. "The local government gave us a place to live closer to town ... but today what we want is justice."

Solano Barillas, now 55, is charged with homicide and crimes against humanity and is the only person facing trial in the case. He was arrested and charged in 2012 after the victims' relatives filed a complaint through the human rights organization Mutual Support Group.

The Mutual Support Group has asked authorities to keep investigating the case and the role of another former guerrilla leader, Pedro Pablo Palma Lau. Rights activists say the man once known as "Commander Pancho" was Solano Barillas' superior.

After the peace accord was signed, Palma Lau, now 62, joined Rios Montt's political party and later became a congressional deputy with the party. He is currently a security consultant for the government and has said he was not in Guatemala when the killings occurred.

For Judge Walter Jimenez, who will preside over Solano Barilla's trial, the court cases are a significant step for Guatemala.